Identification of visual receptor molecule, of the enzyme involved in the growth output (chitin synthetase), and of its mode of regulation are sought. Light induced absorbance changes will be used to monitor indentification of receptor, light control of chitin synthetase to monitor mode of control. Mutants with modified receptors or output regulation will be used as controls. The mutants to be used are in large part on hand and in small part have been classed into groups by tests for complementation of their defects in artificial heterokaryons.